The permeate flux from a spiral-wrap ultrafiltration membrane is a complex function of inlet pressure, reject flowrate, polymer concentration and degree of membrane fouling. A mathematical model is presented that describes the permeate flux before and after the onset of gel-polarisation. The use of the model in evaluating the effects of membrane fouling and cleaning strategies on plant performance is discussed with reference to polyvinyl alcohol textile size recovery. From a network analysis, the optimal configuration of membrane elements shows that significant savings in membrane area and pumping costs are achievable.